The Rock Reservoir Evaluation Of Chang3 Oil Reservoir In Yanwu Area,Ordos Basin

With the large-scale exploration and development in the southwest of the Ordos Basin and the gradual deepening of the understanding of the results in recent years,it is found that the east reserves of Yanwu area in the southwest of the basin are concentrated and have been basically used.Oil reservoirs were discovered in the west of Yanwu area,for example,the industrial oil flow has been obtained by oil test at well points such as Z307 and Z86,which shows a good prospect of exploration and evaluation.However,at present,the study of Chang3 formation in Yanwu area is still very poor,and it is limited to well point research in production test area,and further refining and studying are necessary to the sedimentary micro-facies,the size of sand body,the diagenesis of reservoir,the microscopic characteristics of reservoir and the evaluation of the reservoir.Therefore,this paper takes Chang 3 oil-bearing of Yanchang Formation in Yanwu area,southwest of Ordos Basin,as the research object,throughing core data,logging data,as well as sheet identification,particle size analysis,X-diffraction of clay minerals,scanning electron microscope,high pressure mercury pressure and so on,the comprehensively studing of the petrological characteristics,pore types,pore structure characteristics,diagenesis,diagenetic facies and reservoir physical properties of the reservoir in the study area are finished,and the following conclusions are obtained:1.The rock types of Chang 3 reservoir in this area are mainly gray or light gray meso-fine feldspathic sandstone and lithic sandstone;the interstitial materials are chlorite,kaolinite and other clay minerals;A set of braided river delta sedimentary systems is controlled by southwest provenance,and it can be divided into delta plain subfacies and delta front subfacies,while the subaqueous distributary channel is the main sedimentary reservoir.2.There are three kinds of diagenesis in this area:compaction,cementation and dissolution.The diagenetic stage is in the middle diagenetic stage A;the favorable diagenetic facies of Chang3 is feldspar corrosion-intergranular pores,and chlorite-film cementation-intergranular pores-feldspar corrosion.3.The main pore types of reservoir in this area are intergranular pore,intergranular dissolved pore and intragranular dissolved pore;the pore throat structure is mainly small pore fine throat type,and the pore throat connectivity's level is medium.The average porosity is 12.7%and the average permeability is 5.9×10^-3?m²,so the physical property of rock is poor,which belongs to low porosity and low permeability reservoir,and the reservoir heterogeneity is strong.Reservoir physical properties are controlled by both sedimentary and diagenetic forces.4.Taking sedimentary characteristics,reservoir physical properties,pore types and diagenetic facies as evaluation indexes,basising on these indexes and developing the reservoir comprehensive evaluation,the reservoirs in the study area are divided into three types:type?,class?and type?.The type?reservoir is developed extensively in Chang3 period,and the type?reservoir is locally developed,and the type?reservoir is mainly located on the flank of river channel.